The prior art is replete with structures and disclosures pertaining to hydraulic type brakes for vehicles. These prior art brake units are arranged with provisions for creating hydraulic pressure and applying it to brake members which are thereby displaced and held in a braking position in response to the hydraulic pressure applied thereto. Further, the prior art is aware of hydraulic-type brakes which also employ springs for actuating the brake members when the hydraulic pressure is not available, and two such isolated examples of the prior art are found in U.S. Pat. Nos. 3,613,839 and 3,647,030. Still further, U.S. Pat. No. 3,872,954 discloses an assembly which employes both hydraulic brake elements and principles, and it employs a spring for relieving pressure on clutch plates when there is no hydraulic fluid available for creating the pressure thereon. Also, U.S. Pat. No. 3,547,233 shows a brake assembly with a combination of hydraulic and spring means for controlling and actuating the brake unit, and the same is true for U.S. Pat. No. 3,770,085 and also U.S. Pat. No. 3,863,038 and also U.S. Pat. No. 3,557,913. The aforementioned patents show structures different from the one disclosed herein, and they also show structures which do not perform all the functions performed by the structure of the present invention, and they show structures of apparently lesser capacity than that of the present invention, and this appears to be true of the last-mentioned U.S. Patent.
Accordingly, it is an object of this invention to provide a fail-safe brake for a vehicle which is a general improvement on the structures heretofore known and, more particularly, it provides a unit which performs a greater number of functions and wherein the structure itself is of a greater capacity and more efficient in its operation.
In accomplishing the aforementioned objective, the structure of the present invention utilizes hydraulically-actuated pistons which are guided on a pilot member and which are also guided by a surrounding cylindrical member, with both of those members serving to contain and guide the movable pistons which can therefore have a large capacity for action and are reliable and sensitive in that they will not bind or cock in the structure. Further, the present invention provides the brake structure wherein the hydraulic fluid can be utilized for securing the brake in the engaged or vehicle park condition, and, also, hydraulic fluid can be manually pressurized and utilized for releasing the brake, even though the powered hydraulic pump or its attending brakeline and connections are not operating.
Other objects and advantages will become apparent upon reading the following description in light of the accompanying drawings.